1. Field of the Art
This invention relates to a component of a so-called Ziegler or Ziegler-Natta catalyst for polymerization of olefins.
The catalyst of the present invention is highly active, exhibits very high stereoregularity in the case of production of stereoregular polyolefins, and also provides polymer powder having very uniform distribution of particle sizes.
2. The Prior Art
A variety of the methods for preparation of solid catalyst components wherein magnesium, titanium, a halogen and an electron donor are used as essential components thereof have been proposed. It is also reported that these catalyst components possess generally high polymerization activity and exhibit high stereoregularity in the case of polymerization of an .alpha.-olefin having 3 or more carbon atoms. In these catalyst components, ground or milled magnesium halides are often used as carriers. In these cases, the resulting olefin polymer powder exhibits a broad distribution of particle sizes and comprises a very large proportion of fine powder of about 100 microns or less. Thus, industrial use of such catalyst components are greatly restricted with respect to removal and transportation of polymers and operations of copolymerization in the case of slurry polymerization, or stabilization of flowing states and recovery of polymer powder and the like in the case of gas phase polymerization.
It has also been reported that, to obtain carriers of uniform particle size containing magnesium compounds, a solution of an organomagnesium compound or a solution of a magnesium halide in an electron donor is used as the starting material, and a solid product for the carrier is separated out therefrom. These methods, however, are disadvantageous in that a costly material is required or a special treatment is needed to prevent the solvent electron donor from remaining in the solid catalyst component and producing a harmful action.
Furthermore, a method for obtaining a solid catalyst component for polymerization of olefins has been proposed in Japanese Patent Laid-Open Publication No. 40293/1979. This method utilizes the property of Ti(OR.sup.2).sub.4 of being capable of dissolving Mg(OR.sup.1).sub.2-n X.sub.n and an electron donor (wherein R.sup.1 and R.sup.2 are an alkyl having 1 to 10 carbon atoms, an aryl or a cycloalkyl, X is a halogen and n is a number defined by 0&lt;n.ltoreq.2) and comprises an optional step of separating out a solid product from the solution by cooling it or adding thereto a precipitant and a step of contacting the solution or the separated solid with a liquid titanium halide compound. According to this method, there is provided a process for preparation of a catalyst component at a low cost having a very high activity especially for polymerization of ethylene, without using costly starting material or a harmful electron donor. However, most of these catalysts are useful only as catalysts for production of polyethylene and are not always satisfactory with respect to polymerization activity and stereoregularity in the case of polymerization of an .alpha.-olefin having 3 or more carbon atoms.